Question

If $10\text{g}$ more sugar is added to $120\text{g}$ of $15\%\left(w/w\right)$ aqueous sugar solution, then calculate the concentration $\left(w/w\%\right)$ of the final solution.

• A. $20\%$
• B. $21\%$
• C. $21.5\%$
• D. $23\%$

Answer 1

The correct option is C $21.5\%$

Mass of $15\%\left(w/w\right)$ aqueous sugar solution $=120\text{g}$.
Let mass of solute be $x$
$x/120\times 100=15$
$x=15\times 120/100=18\text{g}$
Final solution has $10\text{g}$ more sugar
Concentration $\left(w/w\right)\%=\frac{18+10}{120+10}\times 100=\frac{28}{130}\times 100$
$=21.5\%$